1. Field of the Invention
The present invention relates to a solid state imaging device in which a color signal and a luminance signal needed to form a color image are simultaneously generated, and an electronic still camera in which such a solid state imaging device is used to reproduce a color image having a high resolution.
2. Description of Related Art
Recently, various electronic still cameras (still video cameras) in which an imaging device for converting an object image to electrical signals and a magnetic disk (video floppy) for recording the electrical signals are used to record a still image in place of a conventional silver salt film have been developed.
FIG. 6 shows an IL-CCD (inter-line type CCD) which is one of the known imaging devices used in electronic still cameras. In an arrangement shown in FIG. 6, a plurality of rows of photosensitive portions 101, each row consisting of a large number of picture elements (photodiodes) 103 which are continuously vertically arranged, and a plurality of rows of vertical transfer portions (vertical transfer CCD's) 105 are alternately arranged side by side. The electrical charges accumulated in the picture elements 103 are transferred to the associated vertical transfer portions 105 at one time, so that the electrical charges which are transferred in the vertical transfer portions 105 in the vertical direction are stepwise transferred to a horizontal transfer portion (not shown). As a result, each line of the electrical charges transferred to the horizontal transfer portions can be read by the horizontal transfer portion.
The photosensitive portions 101 are provided, on their photosensitive surfaces (light receiving surfaces of the picture elements 103), with complementary color filters through which only yellow light (Ye), cyan light (Cy) and magenta light (Mg) can be transmitted, as shown in FIG. 7, or primary color filters through which only red light (R), green light (G) and blue light (B) can be transmitted, as shown in FIG. 8. The color signals for forming a color image are obtained by the electrical charges accumulated in the picture elements 103 which receive light through the color filters.
The vertical transfer portions 105 are provided on their light receiving surfaces, with light intercepting layers, so that only the electrical charges transferred from the photosensitive portions 101 can be accumulated.
However, in comparison with a conventional silver salt picture, an electronic still camera using a solid state imaging device of the kind mentioned above has a low picture quality. In particular, the resolution of the electronic still camera using a solid state imaging device is not comparable to that of the silver salt picture.
In order to increase the resolution, it is necessary to increase the density of the picture elements of the solid state imaging device or to provide separate imaging devices for signal components of red light, green light and blue light (so-called three tube camera).
However, as a matter of course, the provision of a plurality of solid state imaging devices results in a complex and expensive camera.
On the other hand, there are limitations to an increase of the density of the picture elements under modern techniques, and accordingly, it is very difficult to practically realize an inexpensive electronic still camera having a high resolution.